System and method for relay node selection

ABSTRACT

A method for recommending a relay node to which a user agent attaches. The method includes recommending the relay node based on a relay node selection rank.

BACKGROUND

As used herein, the terms “user agent” and “UA” might in some casesrefer to mobile devices such as mobile telephones, personal digitalassistants, handheld or laptop computers, and similar devices that havetelecommunications capabilities. Such a UA might consist of a UA and itsassociated removable memory module, such as but not limited to aUniversal Integrated Circuit Card (UICC) that includes a SubscriberIdentity Module (SIM) application, a Universal Subscriber IdentityModule (USIM) application, or a Removable User Identity Module (R-UIM)application. Alternatively, such a UA might consist of the device itselfwithout such a module. In other cases, the term “UA” might refer todevices that have similar capabilities but that are not transportable,such as desktop computers, set-top boxes, or network appliances. Theterm “UA” can also refer to any hardware or software component that canterminate a communication session for a user. Also, the terms “useragent,” “UA,” “user equipment,” “UE,” “user device” and “user node”might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE). For example, an LTE systemmight include an enhanced node B (eNB), a wireless access point, or asimilar component rather than a traditional base station. As usedherein, the term “access node” will refer to any component of thewireless network, such as a traditional base station, a wireless accesspoint, or an LTE eNB, that creates a geographical area of reception andtransmission coverage allowing a UA or a relay node to access othercomponents in a telecommunications system. In this document, the term“access node” and “access device” may be used interchangeably, but it isunderstood that an access node may comprise a plurality of hardware andsoftware.

The term “access node” does not refer to a “relay node,” which is acomponent in a wireless network that is configured to extend or enhancethe coverage created by an access node or another relay node. The accessnode and relay node are both radio components that may be present in awireless communications network, and the terms “component” and “networknode” may refer to an access node or relay node. It is understood that acomponent might operate as an access node or a relay node depending onits configuration and placement. However, a component is called a “relaynode” only if it requires the wireless coverage of an access node orother relay node to access other components in a wireless communicationssystem. Additionally, two or more relay nodes may used serially toextend or enhance coverage created by an access node.

An LTE system can include protocols such as a Radio Resource Control(RRC) protocol, which is responsible for the assignment, configuration,and release of radio resources between a UA and a network node or otherLTE equipment. The RRC protocol is described in detail in the ThirdGeneration Partnership Project (3GPP) Technical Specification (TS)36.331. According to the RRC protocol, the two basic RRC modes for a UAare defined as “idle mode” and “connected mode.” During the connectedmode or state, the UA may exchange signals with the network and performother related operations, while during the idle mode or state, the UAmay shut down at least some of its connected mode operations. Idle andconnected mode behaviors are described in detail in 3GPP TS 36.304 andTS 36.331.

The signals that carry data between UAs, relay nodes, and access nodescan have frequency, time, and coding parameters and othercharacteristics that might be specified by a network node. A connectionbetween any of these elements that has a specific set of suchcharacteristics can be referred to as a resource. The terms “resource,”“communications connection,” “channel,” and “communications link” mightbe used synonymously herein. A network node typically establishes adifferent resource for each UA or other network node with which it iscommunicating at any particular time.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a diagram illustrating a wireless communication system thatincludes a relay node, according to an embodiment of the disclosure.

FIG. 2 is a diagram illustrating another wireless communication systemthat includes a relay node, according to an embodiment of thedisclosure.

FIG. 3 a is a block diagram of a method for recommending a relay node towhich a user agent attaches according to an embodiment of thedisclosure.

FIG. 3 b is a block diagram of an alternative method for recommending arelay node to which a user agent attaches according to an embodiment ofthe disclosure.

FIG. 4 illustrates a processor and related components suitable forimplementing the several embodiments of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

FIG. 1 is a diagram illustrating a wireless communication system 100using a relay node 102, according to an embodiment of the disclosure.Generally, the present disclosure relates to the use of relay nodes inwireless communications networks. Examples of wireless communicationnetworks include LTE or LTE-Advanced (LTE-A) networks, and all of thedisclosed and claimed embodiments could be implemented in an LTE-Anetwork. The relay node 102 can amplify or repeat a signal received froma UA 110 and cause the modified signal to be received at an access node106. In some implementations of a relay node 102, the relay node 102receives a signal with data from the UA 110 and then generates a newsignal to transmit the data to the access node 106. The relay node 102can also receive data from the access node 106 and deliver the data tothe UA 110. The relay node 102 might be placed near the edges of a cellso that the UA 110 can communicate with the relay node 102 rather thancommunicating directly with the access node 106 for that cell.

In radio systems, a cell is a geographical area of reception andtransmission coverage. Cells can overlap with each other. In the typicalexample, there is one access node associated with each cell. The size ofa cell is determined by factors such as frequency band, power level, andchannel conditions. Relay nodes, such as relay node 102, can be used toenhance coverage within or near a cell, or to extend the size ofcoverage of a cell. Additionally, the use of a relay node 102 canenhance throughput of a signal within a cell because the UA 110 canaccess the relay node 102 at a higher data rate or a lower powertransmission than the UA 110 might use when communicating directly withthe access node 106 for that cell. Transmission at a higher data ratecreates higher spectrum efficiency, and lower power benefits the UA 110by consuming less battery power.

Relay nodes, generally, can be divided into three types: layer one relaynodes, layer two relay nodes, and layer three relay nodes. A layer onerelay node is essentially a repeater that can retransmit a transmissionwithout any modification other than amplification and slight delay. Alayer two relay node can decode a transmission that it receives,re-encode the result of the decoding, and then transmit the re-encodeddata. A layer three relay node can have full radio resource controlcapabilities and can thus function similarly to an access node. Theradio resource control protocols used by a relay node may be the same asthose used by an access node, and the relay node may have a unique cellidentity typically used by an access node. For the purpose of thisdisclosure, a relay node is distinguished from an access node by thefact that it requires the presence of at least one access node (and thecell associated with that access node) or other relay node to accessother components in a telecommunications system. The illustrativeembodiments are primarily concerned with layer two or layer three relaynodes. Therefore, as used herein, the term “relay node” will not referto layer one relay nodes, unless specifically stated otherwise.

In communication system 100, the links that allow wireless communicationcan be said to be of three distinct types. First, when the UA 110 iscommunicating with the access node 106 via the relay node 102, thecommunication link between the UA 110 and the relay node 102 is said tooccur over an access link 108. Second, the communication between therelay node 102 and the access node 106 is said to occur over a relaylink 104. Third, communication that passes directly between the UA 110and the access node 106 without passing through the relay node 102 issaid to occur over a direct link 112. The terms “access link,” “relaylink,” and “direct link” are used in this document according to themeaning described by FIG. 1.

The UA 110 might be a mobile device that can move from one cell toanother. FIG. 2 illustrates a system 200 in which the UA 110 is movingfrom a first cell 210 _(A) covered by a first access node 106 _(A) to asecond cell 210 _(B) covered by a second access node 106 ₈. As the UA110 moves from the first cell 210 _(A) to the second cell 210 ₈, the UA110 might be handed over from the first access node 106 _(A) to thesecond access node 106 ₈. Also, as the UA 110 moves within one of thecells 210, the access node 106 for that cell 210 might cause the UA 110to switch from one carrier to another, from one frequency to another,and/or from one radio access technology (RAT) to another.

Each of the cells 210 contains a plurality of relay nodes 220. Whilefour relay nodes 220 are shown in each of the cells 210, other numbersof relay nodes 220 could be present, and while the areas covered by therelay nodes 220 are not depicted overlapping, the relay node coverageareas might overlap. When the UA 110 is attached to one of the accessnodes 106 via one of the relay nodes 220 and moves out of the coveragearea of that relay node 220, the UA 110 might need to attach to the sameaccess node 106 via another relay node 220 or to another access node 106via another relay node 220.

When a UA is in a cell that has relay nodes, it is sometimes preferablethat the UA connect to the cell's access node via a relay node ratherthan over a direct link. U.S. patent application Ser. No. 12/331,992,filed Dec. 10, 2008, by James Earl Womack, et al, entitled “Method andApparatus for Discovery of Relay Nodes”, which is incorporated herein byreference as if reproduced in its entirety, discusses how a UA candiscover that one or more relay nodes are nearby. The present disclosuredeals with techniques for the UA to evaluate the discovered relay nodesand recommend a relay node to which the UA prefers to attach.

In an embodiment, the behavior of a moving UA differs depending onwhether the UA is in the idle mode or in the connected mode. UA behaviorin the idle mode will be considered first. The UA can save battery lifeby entering the idle mode in which it reduces its communications with anaccess node and monitors a signal that the access node provides. The UAcan also monitor the power levels of other cells to determine whether itshould reselect one of the other cells. An access node can page the UAwhen the access node needs to initiate communication with the UA, andthe UA might then move from the idle mode (or idle state) to theconnected mode (or connected state).

In an embodiment, while in the idle mode, the UA determines the signalstrengths and related parameters of nearby relay nodes and uses thisinformation to recommend which relay node the UA prefers to attach towhen the UA moves from the idle mode to the connected mode. The UA sendsits recommendation to an access node, and the access node can decide toaccept or reject the recommendation.

The relay nodes may not send broadcast signals, but they typically dosend reference symbols on the downlink to the UA. Two measurements havebeen standardized that measure the power of reference symbols. One isreference signal receive power (RSRP), and the other is reference signalreceive quality (RSRQ). RSRP is a linear average of the received powerof the cell-specific reference symbols. RSRQ is the ratio of RSRP andcarrier received signal strength indication (RSSI).

In an embodiment, the UA does not use these measurements alone toevaluate the relay nodes. Instead, these measurements, or a subsetthereof, might be combined with various parameters provided to the UA byan access node to derive a relay node selection rank. For example, thefollowing parameters might be used in any combination to derive therelay node selection rank: an indication of preference or priority, apower offset value, a hysteresis value, an identifier of specific relaynodes, or any metadata about a relay node.

The preference or priority parameter can refer to a relay node that maybe preferable for the UA to attach to, even when other nearby relaynodes have higher signal strengths or other parameters that may seemfavorable. For example, a relay node in a high traffic area such as anairport terminal might have a higher signal strength than other nearbyrelay nodes. However, to prevent overloading the relay node, it may bepreferable that some UAs attach to the other, lower power relay nodes.The relay node in the high traffic area might be assigned a preferenceor priority parameter that decreases the likelihood that a UA willattach to it.

The power offset parameter can refer to the difference in signalstrength between two neighboring relay nodes. When other factors are notconsidered, a UA will generally tend to attach to a relay node that hasa higher signal strength than nearby relay nodes. For example, when a UAattaches to a relay node, in one embodiment it is more efficient for theUA to stay in the current serving relay node unless a neighboring relaynode can provide a higher signal strength. In order for the switch tothe neighboring node to be worth the reconfiguration costs, theneighboring node's signal strength needs to be higher than the servingnode's signal strength by a set amount, i.e., the power offsetparameter. The power offset parameter can be set to zero in some cases.

The hysteresis value is a parameter that can prevent a UA fromfrequently switching back and forth between relay nodes. Due to vagariesin the strengths of relay node signals, a signal from one relay nodethat, at most times, is stronger than the signal from another relay nodemight occasionally be surpassed in strength by the other signal. If a UAalways attached to the relay node with the higher signal strength, theUA might repeatedly alternate the relay node to which it attaches as therelay node with the higher signal strength alternates. To prevent this,a hysteresis value can be specified for a plurality of signal strengthssuch that a UA detaches from a first relay node and attaches to a secondrelay node only when the signal strength of the second relay nodeexceeds the signal strength of the first relay node for a specifiednumber of consecutive measurements, throughout a specified length oftime, or over some other hysteresis range. In one embodiment, when thesignal strength of the neighboring node exceeds the signal strength ofthe serving node by the power offset for the time specified by thehysteresis value, the UA will detach from the serving node and attach tothe neighboring node.

Upon determining the relay node power and receiving these parametersfrom an access node for a plurality of relay nodes, the UA can calculatea relay node selection rank for each of the relay nodes, determine therelay node with the highest relay node selection rank, and inform theaccess node that the UA would prefer to attach to the relay node withhighest relay node selection rank upon leaving the idle mode. That is,an equation such as the following might be calculated in the UA for eachnearby relay node:RN_Reselect(RN)=RSRP(RN)+Preference(RN)+PowerOffset(RN)+Hysteresiswhere RN_Reselect(RN) is the relay node selection rank, RSRP(RN) is themeasured relay node power, Preference(RN) is the preference or priorityparameter for the relay node, PowerOffset(RN) is the power offsetparameter for the relay node, and Hysteresis is the hysteresis parameterfor the relay node. Although Preference(RN), PowerOffset(RN), andHysteresis are described here to be associated with a particular relaynode, other possibilities exist. For example, Preference(RN),PowerOffset(RN), and Hysteresis may be associated with the access nodeassociated with the relay node.

Further, it should be understood that RN_Reselect(RN) is not necessarilycalculated by a simple addition as shown in the equation, but might besome other combination of data related to one or more of RSRP(RN),Preference(RN), PowerOffset(RN), and Hysteresis. For example, any ofthese parameters might be converted to a measurement unit that iscompatible with the other parameters, or any of these parameters mightbe multiplied by a weighting factor to give the parameter a greater orlesser significance. The weighting factor of any of the parameters couldbe set to zero, thus eliminating the parameter from consideration. Thatis, a subset of the parameters could be used. Also, in otherembodiments, other factors might be considered than those above, orother combinations of factors might be considered. An access node mightprovide the Preference(RN), PowerOffset(RN), and Hysteresis values tothe UA through RRC signaling or on a broadcast channel.

To save battery life, an idle UA typically communicates with the networkonly when the UA moves out of a location so that the UA can be paged ifneeded in its new location. However, this may not be an appropriate timeto report relay node power levels and related information, since thereported power level information is only relevant when the UA moves intothe connected mode from the idle mode. In an embodiment, the identity ofthe relay node that the UA prefers based on the RN_Reselect(RN) value isreported to the access node when the UA is changing from the idle modeto the connected mode. In an embodiment, the identity of the relay nodeis included in an RRC Connection Setup Complete message or anotherrelevant RRC uplink message that the UA sends to the access node.

When the UA is in the connected mode, a similar relay node measurementprocedure and relay node ranking procedure may be applied. This could beinitiated by a Radio Resource Control message from the network node orby a mode change of the UA (i.e., switching from the idle mode to theconnected mode). For example, when the UA switches from the idle mode tothe connected mode, the UA could start to monitor nearby relay nodes andperform a relay node ranking procedure. The UA could then report theresults to a network node, i.e., the access node. In one embodiment, theUA recommends a relay node to which to attach based on the rankingprocedure and reports the recommended relay node to the access node. Theaccess node may or may not override the UA's recommendation. In anotherembodiment, the UA reports the candidates and their relative ranking,and the access node selects the relay node to which the UA connects. Inan embodiment, a Measurement Report message is used for the UA'sreporting. In the connected mode, the UA may continue monitoring therelay nodes and perform the ranking procedure and update the recommendedrelay node. Alternatively, the UA may monitor the nearby relay nodesonly when it switches from the idle mode to the connected mode.

In an embodiment, when the UA is in the connected mode and attached to arelay node, the UA is not handed over from the relay node to anotherrelay node, another cell, another network, another frequency, or anotherRAT. Instead, the UA is first handed over from the relay node to theaccess node associated with the relay node. The access node then handsthe UA over to the other relay node, cell, network, frequency, or RAT.When the UA is handed over to another relay node, the relay node towhich the UA is handed over might be selected based on the relay nodeselection rank as described above. In an example signaling flow, theaccess node first sends a Measurement Control Message to the UA, whichmay include the IDs of the nearby relay nodes, measurementconfigurations, etc. Then the UA may perform the measurement proceduresand, based on the ranking procedure, the UA may send a Handover Requestmessage to the access node which may include the ID of the candidaterelay node that the UA wishes to switch to. After the access nodereceives the Handover Request message, the access node may accept therelay node handover request and send a Handover Command to the UA. Thenthe UA may start to access the target relay node using the informationprovided in the Handover Command message.

In another embodiment, when the UA is in the connected mode, the UA ishanded over from a relay node directly to another relay node, anothercell, another network, another frequency, or another RAT. In an examplesignaling flow, after the UA performs the relay node ranking and atarget relay node is selected, the UA may directly access the targetrelay node. After the target relay node receives an access message, thetarget relay node may notify the access node and, if the access nodeaccepts the handover, the target relay node will send an access responseto the UA indicating the successful relay handover.

FIG. 3 a illustrates an embodiment of a method 300 for recommending arelay node to which a UA attaches. In block 310, a relay node isrecommended based on a relay node selection rank.

FIG. 3 b illustrates an embodiment of an alternative method 350 forrecommending a relay node to which a UA attaches. In block 360, when theUA is in the connected mode, the UA is handed over to the relay nodeafter the UA is handed over to an access node.

The UA 110 and other components described above might include aprocessing component that is capable of executing instructions relatedto the actions described above. FIG. 4 illustrates an example of asystem 1300 that includes a processing component 1310 suitable forimplementing one or more embodiments disclosed herein. In addition tothe processor 1310 (which may be referred to as a central processor unitor CPU), the system 1300 might include network connectivity devices1320, random access memory (RAM) 1330, read only memory (ROM) 1340,secondary storage 1350, and input/output (I/O) devices 1360. Thesecomponents might communicate with one another via a bus 1370. In somecases, some of these components may not be present or may be combined invarious combinations with one another or with other components notshown. These components might be located in a single physical entity orin more than one physical entity. Any actions described herein as beingtaken by the processor 1310 might be taken by the processor 1310 aloneor by the processor 1310 in conjunction with one or more componentsshown or not shown in the drawing, such as a digital signal processor(DSP) 502. Although the DSP 502 is shown as a separate component, theDSP 502 might be incorporated into the processor 1310.

The processor 1310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 1320,RAM 1330, ROM 1340, or secondary storage 1350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 1310 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 1310 may beimplemented as one or more CPU chips.

The network connectivity devices 1320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 1320 may enable the processor 1310 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 1310 might receiveinformation or to which the processor 1310 might output information. Thenetwork connectivity devices 1320 might also include one or moretransceiver components 1325 capable of transmitting and/or receivingdata wirelessly.

The RAM 1330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 1310. The ROM 1340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 1350. ROM 1340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 1330 and ROM 1340 istypically faster than to secondary storage 1350. The secondary storage1350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 1330 is not large enough to hold all workingdata. Secondary storage 1350 may be used to store programs that areloaded into RAM 1330 when such programs are selected for execution.

The I/O devices 1360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input devices. Also, the transceiver 1325might be considered to be a component of the I/O devices 1360 instead ofor in addition to being a component of the network connectivity devices1320.

In an embodiment, a method is provided for recommending a relay node towhich a user agent attaches. The method includes recommending the relaynode based on a relay node selection rank.

In another embodiment, another method is provided for recommending arelay node to which a user agent attaches. The method includes, when theuser agent is in a connected mode, handing the user agent over to therelay node after handing the user agent over to an access node.

In another embodiment, a user agent is provided that includes aprocessor configured to recommend a relay node based on a relay nodeselection rank.

In another embodiment, a wireless communication system is provided. Thesystem includes a component configured to receive an identity of a relaynode recommended based on a relay node selection rank and to promoteattaching a user agent to the relay node.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the scopeof the present disclosure. The present examples are to be considered asillustrative and not restrictive, and the intention is not to be limitedto the details given herein. For example, the various elements orcomponents may be combined or integrated in another system or certainfeatures may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for operating a user agent in a wirelesscommunication network, the method comprising: calculating, by the useragent, a relay node selection rank for a plurality of relay nodes,ranking, by the user agent, the plurality of relay nodes based on thecalculated ranks, wherein the user agent ranks the plurality of relaynodes during an idle mode; recommending, by the user agent, a relay nodeto an access node based on the ranking, wherein the user agentrecommends the relay node when the user agent switches from the idlemode to a connected mode; and after the user agent ranking the pluralityof relay nodes during the idle mode, re-ranking, by the user agent, theplurality of relay nodes upon receiving a message from the access nodeto initiate a relay node ranking procedure, wherein the user agentre-ranks the plurality of relay nodes during the connected mode.
 2. Themethod of claim 1, wherein the user agent informs the access node of therecommendation in a Radio Resource Control (RRC) Connection SetupComplete message.
 3. The method of claim 1, further comprising receivingat least one of a preference parameter, a power offset parameter, and ahysteresis parameter from the access node in at least one of: radioresource control signaling; and a broadcast channel.
 4. The method ofclaim 3, wherein calculating the relay node selection rank is based onat least one of the preference parameter or the hysteresis parameter. 5.The method of claim 3, wherein calculating the relay node selection rankcomprises: using a reference signal receive power; and applying aweighting factor to at least one of the reference receive signal power,the preference parameter, the power offset parameter, or the hysteresisparameter.
 6. The method of claim 1, wherein the user agent calculatesthe relay node selection rank for the plurality of relay nodes based atleast partly on signal strength of the plurality of relay nodes.
 7. Themethod of claim 6, wherein the user agent ranks each relay node amongthe plurality of relay nodes regardless of whether the signal strengthof each respective relay node exceeds a predetermined threshold.
 8. Themethod of claim 6, wherein the user agent detaches from a first relaynode and attaches to a second relay node only when the signal strengthof the second relay node exceeds the signal strength of the first relaynode by a power offset parameter for a predetermined number ofconsecutive signal strength measurements or throughout a predeterminedlength of time.
 9. The method of claim 1, wherein the user agentrecommends a new relay node based on the relay node ranking procedurethat occurs upon the user agent receiving the message from the accessnode to trigger the relay node ranking procedure.
 10. The method ofclaim 1, wherein the recommendation informs the access node which of theplurality of relay nodes the user agent prefers to attach to uponleaving the idle mode.
 11. The method of claim 10, further comprising:when the user agent switches from the idle mode to the connected mode,handing the user agent over to the recommended relay node only if theaccess node accepts the recommendation.
 12. A user agent, comprising: aprocessor configured to: calculate a relay node selection rank for aplurality of relay nodes; rank the plurality of relay nodes based on thecalculated ranks, wherein the processor ranks the plurality of relaynodes while the user agent is in an idle mode; recommend the relay nodeto an access node based on the ranking, wherein the processor recommendsthe relay node when the user agent switches from the idle mode to aconnected mode; and after ranking the plurality of relay nodes while theuser agent was in the idle mode, re-rank the plurality of relay nodesupon receiving a message from the access node to initiate a relay noderanking procedure, wherein the user agent re-ranks the plurality ofrelay nodes during the connected mode.
 13. The user agent of claim 12,wherein the user agent informs the access node of the recommendation ina Radio Resource Control (RRC) Connection Setup Complete message. 14.The user agent of claim 12, wherein the user agent receives at least oneof a preference parameter, a power offset parameter, and a hysteresisparameter from the access node in at least one of: radio resourcecontrol signaling; and a broadcast channel.
 15. The user agent of claim14, wherein the processor calculates the relay node selection rank basedon at least one of the preference parameter or the hysteresis parameter.16. The user agent of claim 14, wherein the processor calculates therelay node selection rank using a reference receive signal power, and byapplying a weighting factor to at least one of the reference receivesignal power, the preference parameter, the power offset parameter, orthe hysteresis parameter.
 17. The user agent of claim 12, wherein theprocessor is configured to recommend a new relay node based on the relaynode ranking procedure that occurs upon the user agent receiving themessage from the access node to trigger the relay node rankingprocedure.
 18. The user agent of claim 12, wherein the processor isfurther configured, when the user agent is in the connected mode andattached to a first relay node, to promote handing the user agent overto a second relay node after the user agent is handed over to an accessnode associated with the first relay node.
 19. The user agent of claim12, wherein the user agent calculates the relay node selection rank forthe plurality of relay nodes based at least partly on signal strength ofthe plurality of relay nodes.
 20. The user agent of claim 19, whereinthe user agent ranks each relay node among the plurality of relay nodesregardless of whether the signal strength of each respective relay nodeexceeds a predetermined threshold.
 21. The user agent of claim 19,wherein the user agent detaches from a first relay node and attaches toa second relay node only when the signal strength of the second relaynode exceeds the signal strength of the first relay node by a poweroffset parameter for a predetermined number of consecutive signalstrength measurements or throughout a predetermined length of time. 22.The user agent of claim 12, wherein the processor re-ranks the pluralityof relay nodes while the user agent is in the connected mode, andwherein the recommendation informs the access node which of theplurality of relay nodes the user agent prefers to attach to uponleaving the idle mode.
 23. The user agent of claim 22, wherein when theuser agent moves from the idle mode to the connected mode, the processorpromotes attaching the user agent to the recommended relay node only ifthe access node does not override the recommendation.